This invention relates to linear compounds in the form of oligomers or polymers containing unsubstituted or substituted phenol units and unsubstituted or substituted salicylic acid units. These compounds are useful as additives for lubricants and fuels. Metal salts of these compounds are useful as lubricant additives.
In high speed aircraft, both civilian and military, the liquid fuel is combusted to produce power, but also is circulated in the aircraft as a heat exchange fluid to remove the excess heat generated at such speeds from other fluids such as lubricating oils used in the aircraft. The fuel is thus maintained for long periods at high temperatures. This results in discoloration and decomposition which produce soluble colored products and insoluble products such as gums, sediments and granular material. The insoluble products can form deposits that reduce the heat exchange capacity and can block filters potentially causing loss of power. Soluble colored by-products are unsightly and an indication of decomposition.
In some oil fired devices, such as boilers and slow heating cookers, e.g. the Aga type, kerosene fuel is passed down a narrow metal feed pipe to the combustion chamber where it is burnt. Parts of the pipe are sufficiently near the hot chamber for them to be heated to significant temperatures, resulting in the risk of thermal degradation of the fuel in the pipe, especially with slow feed rates and high residence times in the pipe. This degradation can form solid deposits which reduce the flow and ultimately stop it, causing the combustion to stop. To overcome this manufactures of such devices have for many years recommended to their users that at least once each six months such pipe parts are cleaned of solid deposits of coke or other materials.
The problem therefore is to provide enhanced thermal stability to these fuels. The present invention provides a solution to this problem. The addition of the inventive compounds to these fuels enhances the thermal stability of such fuels.
International publications WO 99/25677 and WO 99/25793 disclose calixarenes containing within the calixarene ring at least one salicylic acid. The use of these compounds as fuel additives and lubricant additives is disclosed. Metal salts of these compounds as well as the use of such metal salts as lubricant additives are disclosed. These references indicate that in order to provide the calixarene ring structure it is necessary to use a reaction mixture containing at least 50% by weight solvent, preferably at least 80% by weight solvent, more preferably at least 90% by weight solvent. The references indicate that at solvent concentrations well below 50% by weight linear molecules are formed.
This invention relates to a linear compound comprising m units of formula (I) 
and n units of the formula (II) 
joined together, each end of the compound having a terminal group which is independently one of the following 
wherein in formulae (I)-(IV), Y is a divalent bridging group which may be the same or different in each unit; R0 is hydrogen or a hydrocarbyl group, R5 is hydrogen or a hydrocarbyl, j is 1 or 2; R3 is hydrogen, a hydrocarbyl or a hetero-substituted hydrocarbyl group; either R1 is hydroxyl and R2 and R4 are independently either hydrogen, hydrocarbyl or hetero-substituted hydrocarbyl, or R2 and R4 are hydroxyl and R1 is either hydrogen, hydrocarbyl or hetero-substituted hydrocarbyl; m is at least 1; n is at least 2; the ratio of m to n ranges from about 0.1:1 to about 2:1, the total of m+n is at least 3; the linear compound containing at least one block unit containing at least two units corresponding to formula (II) attached to each other, the linear compound being formed in a reaction mixture optionally containing an organic solvent, the concentration of the organic solvent in the reaction mixture being up to about 48% by weight of the reaction mixture. The invention further provides for metal salts of the foregoing compounds. The linear compounds are useful as fuel and lubricant additives. The salts are useful as lubricant additives.
The inventive linear compounds, at least in one embodiment, are useful in the inventive lubricating oil compositions as surfactants and/or antioxidants. They are useful in the inventive fuel compositions, at least in one embodiment, as thermal stabilizers.
The metal salts of the inventive linear compounds are useful in the inventive lubricating oil compositions, at least in one embodiment, as detergents. The metal salts are also useful, at least in one embodiment, in reducing black paint in low- or medium-speed diesel engines.